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Description
Introduction
Microtia and traumatic injuries are among the primary causes of external ear malformation or absence. Based on epidemiological data, approximately 1.46 out of every 10,000 newborns are affected by microtia, with 22.1% of these cases involving complete anotia [1]. To address these conditions, different ear reconstruction approaches have been developed, including autologous rib cartilage grafts, silicone prostheses, and tissue-engineered polymeric implants [2]. This study presents a novel, patient-specific strategy, involving the design and fabrication of a 3D-printed porous scaffold composed of thermoplastic polyurethane (TPU) and polycaprolactone (PCL).
Materials and Methods
TPU and PCL were selected for their mechanical compatibility with external ear tissues. PCL mimics the auricular cartilage, while TPU replicates the ear lobe’s adipose tissue. 3D printing parameters were optimized to achieve the desired porosity and mechanical performance. A laser scanner was used to capture the geometry of the patient's healthy ear. The scanned image was processed to generate a 3D model. The model was split into two parts: the ear lobe and base (TPU printed) and the helix, anti-helix, and concha (PCL printed). MicroCT scans was used to analyze scaffold architecture, including pore size and interconnectivity, and filament dimensions and distribution. DMA was used to evaluate the compressive and torsional properties, with the aim of matching them to the mechanical characteristics of the native auricular cartilage and adipose tissue. Scaffold cytocompatibility was assessed through cell viability and proliferation assays up to 21 days. CondroISO-9 chondrocytes were seeded on PCL scaffold, and 3T3-L1 pre-adipocytes on the TPU one. Cell viability was evaluated by AlamarBlue assay, cell proliferation with DAPI staining. SEM imaging provided qualitative insights into cells morphology and distribution. Adipocytes differentiation and functionality was evaluated by Nile Red staining, evidencing intracellular lipidic droplets.
Results and Discussion
Optimized printing parameters resulted in scaffolds with accurate filament diameter and uniform layer height. The average pore size (390 μm) was suitable for cartilage and adipose tissue regeneration. Compression tests confirmed TPU is the most deformable material with lower elastic modulus, while PCL and the stratified samples exhibited similar mechanical behavior, with the former having a slightly lower elastic modulus. Torsional test highlighted that TPU showed a high flexibility, with the lowest storage and loss moduli. In this case, the material that appears to offer the most resistance to torsion is PCL, and the stratified samples have a behavior that lies in between TPU and PCL, more towards the softer one. Both chondrocytes and preadipocytes seeded respectively on PCL and TPU showed an increasing trend in cell viability up to 21 days. Differentiated adipocytes showed enhanced viability compared to non-differentiated ones, and lipidic droplets production starting from day 14.
Conclusion
This study demonstrates the potential of patient-specific, 3D-printed scaffolds composed of biocompatible polymers as an innovative solution for ear reconstruction in cases of microtia and anotia. This approach offers a promising alternative to conventional surgical methods by combining anatomical precision and tissue-specific mechanics.
References
[1] Baluch N, et al. Plast Surg. 2014;22(1):39-43.
[2] Oh SH, et al. Biomacromolecules. 2010;11(8):1948-55.
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